The nightmares started right after Dominique Petit’s daughter was born.

The first-time mom would dream that something horrible had happened to her baby and without ever waking she'd bolt upright and start searching for the infant.

“I was dreaming she was lost in the sheets,” Petit, now 45, remembers. “Or that I had rolled on top of her and was squishing her. I would go through the movements of looking through the bedding to see where she was.”

The dreams were so intense, disturbing and realistic that upon waking, Petit always needed to rush to her daughter’s room to make sure the infant was safe. “The fastest way to relieve the anxiety was to see her in her own crib,” she remembers.

Petit’s husband, sleep researcher Tore Nielsen, was intrigued. He wondered whether other new mothers commonly experienced these kinds of nightmares and movements during sleep. A quick poll of family members who’d recently given birth suggested he was on to something: nine out of 10 moms told of strange sleep experiences.

So Nielsen, a professor in the department of psychiatry at the University of Montreal and researcher at the Dream and Nightmare Laboratory at the Hopital du Sacre-Coeur de Montreal, decided to document this phenomenon for the sake of science.

He rounded up 202 new mothers who were being seen at the hospital and questioned them about their dreams and sleep behaviors. For comparison, Nielsen also surveyed 50 pregnant women and 21 who’d never had a baby.

Sure enough, almost three-quarters of women who’d recently given birth reported being plagued by terrifying nightmares involving their infants, according to the study published this month in the journal Sleep.

Bedtime anxieties
A similar percentage reported anxiety-ridden dreams. This is compared to 59 percent of pregnant women and 42 percent of those who’d never had a child.

Pregnant women’s nightmares often involved miscarriages or still births. One woman remembered a ghastly dream in which the baby’s foot started coming out of her belly. She woke up, frightened and horrified, with her hands pushing against her belly. Another told of a dream of a highway accident she feared would kill her baby.

After the baby arrived, some new moms dreamed that they’d dropped the baby or that their infant had died while in the care of a babysitter. Others dreamed that their babies had morphed and now had four eyes.

Rates of women who are opting for preventive mastectomies, such as Angeline Jolie, have increased by an estimated 50 percent in recent years, experts say. But many doctors are puzzled because the operation doesn't carry a 100 percent guarantee, it's major surgery -- and women have other options, from a once-a-day pill to careful monitoring.

Dr. Sheldon Roth suspects that the dreams reflect the anxiety that new, inexperienced parents feel when their first child is born. For nine months, moms know exactly where their baby is, says Roth, a clinical assistant professor of psychiatry at the Harvard Medical School and a dream expert.

People use dreams as a way of problem solving and adapting to new circumstances, Roth says. These parents are simply using their dreams to mentally sort out a huge life change.

For his part, Nielsen theorizes that the nightmares experienced by his wife and other new moms might be in some way related to how the brain builds attachments to a new baby. He doesn’t think that hormones have much to do with the nightmares because some new dads he’s talked to have experienced the same thing.

Case of the missing baby
Many researchers now think that new memories — especially emotionally charged ones — are organized and stored during sleep, Nielsen says.

“What I think is happening is that during the first few weeks the mother and father are building mental representations of the child,” he explains. “For example, it’s possible that as the memory traces are being laid down, they’re not so stable, so you get dreams in which the baby is suddenly gone.”

As for the strange sleep behaviors (known as parasomnias) such as digging for baby in the sheets, Nielsen attributes these to fragmented sleep and the high anxiety levels of new parents who worry they won’t do everything perfectly.

Certain people are born with a tendency to be up and about while unconscious, Collop says. But lack of sleep, coupled with anxiety can bring on these parasomnias.

Nielsen can’t say how long the nightmares will last. His study followed women for just three months and many were still experiencing anxious dreams at the end of the study. He says he’d like to go back and check with the women to answer this question.

Petit says her nightmares trailed off after a couple of months. Now, she’s back to peaceful nights and sweet dreams — at least until her daughter hits the teenage years.

Linda Carroll is a health and science writer living in New Jersey. Her work has appeared in The New York Times, Newsday, Health magazine and SmartMoney.